The present invention relates to a composite polishing pad for use in an apparatus for the linear chemical mechanical planarization of surfaces such as semiconductor wafers.
Chemical mechanical planarization (CMP) is a process used to planarize raw semiconductor wafers and each layer of material added to the semiconductor wafer thereafter. Conventional CMP systems often use a rotating wafer holder that brings the semiconductor wafer into contact with a polishing pad. The polishing pad moves in the plane of the semiconductor wafer surface to be polished. A polishing fluid, such as a chemical polishing agent or slurry containing microabrasives, is applied to the polishing pad. The wafer holder then presses the semiconductor wafer against the rotating polishing pad, and polishing commences.
Commercially available polishing pads come in a variety of hardnesses. Softer polishing pads have certain advantages. Softer polishing pads can more easily conform to the different features on the wafer and tend to achieve global planarity. Also, they tend to scratch the surface of the semiconductor wafer less than hard pads. Soft polishing pads also provide a better vehicle than hard polishing pads for delivering slurry to the polishing site because the slurry can soak into the soft polishing pad material. Soft polishing pads do, however, have some disadvantages. Although they achieve better global planarity, it is done at the expense of local planarity. Also, soft polishing pads tend to polish away material more slowly, given the same speed and pressure as a hard polishing pad. Harder polishing pads, although they achieve better local planarity, achieve that result at the expense of global planarity.
Composite polishing pads have been created to attempt to combine the best features of soft and hard polishing pads. Two examples are xe2x80x9csandwichxe2x80x9d types, which use vertical stacking of hard and soft layers (U.S. Pat. No. 5,212,910 to Breivogel, et al., hereby incorporated by reference), and xe2x80x9cdistributedxe2x80x9d types which attach hard pieces to a soft support layer (U.S. Pat. No. 5,230,184 to Bukhman, hereby incorporated by reference).
These types of composite polishing pads tend to degrade easily over time as the polishing pads wear. The soft material tends to lose its elasticity, and the composite pad becomes loaded with polish residuals and slurry, Further, in the sandwich polishing pads, the hard polishing pad layer tends to split apart from the soft polishing pad layer as a result of wear and tear. Thus, the polishing pad life is shortened.
Accordingly, there remains a need for a composite polishing pad that provides uniform planarity, extended pad life, and good slurry delivery.
The composite polishing pads and the methods disclosed herein solve at least some of the problems left unsolved by conventional polishing pads.
In one aspect of the invention, a composite polishing pad for use in a linear chemical-mechanical polishing apparatus is provided. The pad has a hard polishing pad having a polishing surface and an attachment surface opposite the polishing surface. The attachment surface has a border comprising an adhesive, and the border surrounds a cavity. The cavity is sized and shaped to receive a soft polishing pad. The soft polishing pad is disposed completely in the cavity and completely filling the cavity. The soft polishing pad has a first side adhered in the cavity of the hard polishing pad, and a second side comprising an adhesive, such that the attachment surface of the hard polishing pad and the second side of the soft polishing pad are substantially in a common plane.
In another aspect of the invention, a composite polishing pad includes a hard polishing pad having a polishing surface and an attachment surface opposite the polishing surface, the attachment surface comprising a border comprising an adhesive, the border surrounding a cavity. The cavity is adapted to receive a soft polishing pad; the soft polishing pad disposed completely in the cavity and completely filling the cavity. The soft polishing pad has a first side adhered in the cavity of the hard polishing pad and a second side comprising an adhesive, whereby the attachment surface of the hard polishing pad and the second side of the soft polishing pad are substantially in a common plane. The composite polishing pad is adhered to a belt in the linear chemical-mechanical polishing apparatus.
In still another aspect of the invention, a composite polishing pad includes a hard polishing pad of a certain length having a polishing surface and an attachment surface opposite the polishing surface, the attachment surface comprising an adhesive; a soft polishing pad of a length less than the length of the hard polishing pad, the soft polishing pad having a first side adhered to a first portion of the attachment surface of the hard polishing pad, and the soft polishing pad having a second side comprising an adhesive; and a steel belt in the linear chemical-mechanical polishing apparatus adhered to the second side of the soft polishing pad and to a second portion the attachment surface of the hard polishing pad.
In still another aspect of the invention, a method of making a composite polishing pad is provided. The method comprises (a) providing a hard polishing pad having a polishing side and an attachment side opposite the polishing side, the attachment side comprising an adhesive; (b) shaping the attachment side to form a border surrounding a cavity that is adapted to receive a soft polishing pad therein; (c) inserting the soft polishing pad into the cavity, the soft polishing pad being completely within the cavity and filling the cavity; and (d) adhering the soft polishing pad in the cavity.
In still another aspect of the invention, another method if making a composite polishing pad comprises: (a) providing a hard polishing pad of a predetermined length having a polishing side and having an attachment side opposite the polishing side, the attachment side comprising an adhesive; (b) providing a soft polishing pad of a length shorter than the length of the hard polishing pad, the soft polishing pad having a first side comprising an adhesive and a second side comprising an adhesive; (c) providing a belt in a linear apparatus for chemical-mechanical polishing; (d) adhering the second side of the soft polishing pad to the belt; (e) adhering a first portion of the attachment side of the hard polishing pad to the soft polishing pad; and (e adhering a second portion of the attachment side of the hard polishing pad to the belt.
In yet another aspect of the invention, a method of preventing a composite polishing pad from splitting apart is provided. The method comprises: (a) providing a hard polishing pad having a polishing side and an attachment side opposite the polishing side, the attachment side comprising an adhesive; (b) shaping the attachment side to form a border surrounding a cavity that is adapted to receive a soft polishing pad therein; (c) inserting the soft polishing pad into the cavity, the soft polishing pad being completely within the cavity and filling the cavity; (d) adhering the soft polishing pad in the cavity to form a composite pad; and (e) adhering the composite pad to a belt in a linear chemical-mechanical polishing apparatus such that the border adheres to the belt and the soft polishing pad adheres to the belt.
The present invention provides the foregoing and other features, and the advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention and do not limit the scope of the invention, which is defined by the appended claims and equivalents thereof.